1. Field of the Invention
The present invention generally pertains to a method and system for controlling the flow of fruit and fruit juice through a juice extraction facility, and more particularly, it pertains to a method and system for providing the optimal number of fruit to the extraction facility at all times.
2. Description of the Prior Art
The production of juice and other products from whole citrus fruit has become a major industry in the United States. Large citrus processing plants produce a variety of products from citrus fruit including fresh citrus juice, frozen concentrated citrus juice, citrus peel oil, citrus flavoring, and dried pulp for cattle feed. The heart of any such processing plant is the juice extraction facility wherein primary separation is achieved between the juice and juice cells on the one hand and remaining portions of the citrus fruit on the other hand. The juice and juice cells are discharged into a juice storage tank and thereafter directed to a finisher wherein excess juice cells are removed. The pure juice may then be canned, frozen or marketed fresh, as desired. The remaining portions of fruit, including the peel, peel oil, seeds, core material and membrane material, are processed further to produce the other products.
The actual separation of the juice and juice cells from the remainder of the whole fruit is accomplished by a number of juice extraction machines, usually called extractors. These extractors, described in detail hereinafter, are each adapted to receive fruit in a particular range of sizes. It is necessary therefore, to separate the fruit into size categories prior to feeding the rate to the extractors. With this in mind, the operations within a typical juice extraction facility will be explained.
Reference will now be made to FIG. 1 which illustrates the layout of equipment in a typical juice extraction facility. Fruit F is stored in bulk in a storage bin 10 which receives freshly harvested fruit by the truckload from the citrus grove. In addition to such raw fruit, a stream of recycled fruit is directed to the storage bin 10, as described hereinafter. A feed conveyor 12, driven by a variable speed motor 13, withdraws fruit from the bottom of the storage bin 10. From the feed conveyor 12, the fruit is deposited on a washing conveyor 14 where said fruit is washed by plurality of overhead water spray nozzles 15. The fruit next proceeds to a sorting conveyor 16 where unesirable fruit are manually removed from the feed stream.
After being washed and manually sorted, the fruit F is automatically separated according to size by a sizer 18. The sizer 18 divides the fruit F into two or more size categories corresponding to the size ranges of the extractors. Sizer 18 in FIG. 1 is shown to divide the fruit into two categories, i.e., small (below 3 inch diameter) and large (3 to 4 inch diameter). Oversize fruit with a diameter larger than 4 inches is directed away from the process stream. It will be understood, however, that the present invention is applicable to a system with any number of size categories.
The sizer 18 may be of any type capable of segregating the fruit into the size categories mentioned. One such sizer that has been found adequate is a "belt and roll sizer". In such a sizer, fruit is fed down two or more sizing runs. Each sizing run comprises a feed belt positioned adjacent a roller bar. The distance between the belt and the roller bar determines the size of the fruit which falls down to an associated discharge conveyor, with one discharge conveyor corresponding to each of the size categories. In sizer 18, a first sizing run is adjusted to allow fruit of 3" diameter and smaller to drop to a first discharge conveyor and a second sizing run allows fruit 4" diameter and smaller to drop to a second discharge conveyor. Fruit larger than 4" is removed by the oversize fruit discharge conveyor (not shown). Adjustment of the distance between the roller and the conveyor of the first sizing run adjusts the cut point beteen the large and small size categories and is accomplished by rotating a sizer adjustment shaft 19.
From the sizer 18, the fruit F is removed on two tilted-belt discharge conveyors 20, 21. These conveyors are adapted to feed the fruit F to a plurality of individual juice extracting machines 23, 24, as discussed hereinafter. The belts are each tilted toward the side where the extractors are located so that the fruit will gather along that side. A retaining wall 26 (see FIG. 4) disposed at the lower side of each conveyor 20, 21 prevents the fruit F from falling off the conveyor belt. The wall 26 has an opening associated with each of the extractors to allow the fruit F to feed into that extractor. It will be appreciated that the number of fruit carried by the tilted-belt conveyor diminishes along the length of the conveyor as individual fruit are consumed by the extractors. Ideally, the precise number of fruit will enter each conveyor so that all extractors have fruit available at all time with a small excess of fruit to insure proper feed to the final extractor. Provisions are made at the end of each tilted-belt conveyor 20, 21 to drop the fruit to a recycle conveyor 70 (see FIG. 4) disposed below the tilted-belt conveyor, which recycle conveyor returns the unused fruit to the storage bin 10.
The juice extractors 23, 24 are each equipped with a plurality of individual cups of a preselected size, each cup being adapted to extract the juice from a single piece of fruit at a time. In the juice room of FIG. 1, four small extractors 23 are grouped together to receive the smaller fruit carried by conveyor 20. Each extractor 23 has five cups which together can process over 300 fruit per minute. Similarly, four large extractors 24 are grouped to receive the larger fruit from conveyor 21. Each extractor is powered by an extractor drive motor 35.
The operation of both the small extractors 23 and the large extractors 24 is the same. Fruit is fed singly from the tilted-belt conveyors 20, 21 into the extracting cups of the extractors. Each piece of fruit is received by a stationary lower cup which automatically centers and positions it for extraction. An upper cup descends, and as numerous metal fingers of the two cups intermesh, pressure is applied evenly to all surfaces of the fruit. The bottom of the lower cup contains a stainless steel cutter tube leading to the finishing tube and manifold. The cutter tube cuts a small circular plug in the bottom of the fruit, and as pressure is applied by the cups, the complete inside of the fruit is pressed into the finishing tube where the juice and juice cells are instantaneously separated from the seeds and section membrane. Only pure juice and juice cells are discharged into the juice collection system, as described hereinafter. The construction and operation of such extractors are explained in the patents to Belk et al, U.S. Pat. No. 2,780,988 and to Hait, U.S. Pat. No. 2,649,730.
Extractors of a given size are grouped together and arranged to receive fruit within the particular size category. The extractor facility disclosed in FIG. 1, includes two groups of four extractors 23, 24, one group associated with each of the two tilted-belt conveyors 20, 21. Juice outlet lines from each of the extractors 23, 24 are joined together in the juice manifold system 27 and the juice from all extractors is fed to a juice storage tank 28.
Juice extraction facilities, such as the one described hereinbefore, have heretofore been controlled manually. From a control room, the user has been able to view the fruit flow down each of the tilted-belt discharge conveyors. A remote indication of the juice level in the juice storage tank is also available. The control options have been limited. First, the user could turn down the feed rate from the fruit storage location when it is obvious that an excess amount of fruit is being recycled from either or both of the tilted-belt conveyors. Second, when one conveyor is carrying a disproportionately large share of the fruit, it was possible to adjust the size to balance the flows. This adjustment was difficult, however, since the effect was not observed until some time after the adjustment was made. The final control option heretofore was to turn off and on individual extractors as required. The user could turn off extractors when the level in the juice tank was high, or when extractors in a given size category was receiving an inadequate number of fruit. The user could turn on extractors when the juice level was low, or excess fruit was being recycled from a given group of extractors. With such manual control, it was impossible to optimize operation to achieve maximum product output with minimum power consumption.
There has long been a desire to provide an automatic control system to optimize the flow of fruit and fruit juice in a juice extraction facility. The advantages of such optimization would be to (1) reduce power consumption by running extractors only when sufficient fruit is available to feed each extractor, (2) avoid damage to fruit through excessive recycling, and (3) balance the flow between different groups of extractors by properly adjusting the cut point between fruit size grades going to each extractor line whereby maximum utilization of extractors is achieved.
Control of the juice extraction facility presents a number of unique problems. Simply measuring the fruit flow of each of the tilted-belt conveyors proves to be a difficult task. Moreover, the transport delays between making an adjustment and observing the effects of said adjustment further complicate the control scheme. For example, the time delay between shutting down an extractor and observing a reduced juice flow to the juice tank is in the order of several minutes. The time delay between adjusting the sizer and observing the load change in fruit carried by each of the several conveyors is also in the order of minutes. Finally, the time lag between changing the feed rate of fruit from the fruit storage location and observing that change in the number of fruit fed to the extractors may be as long as two minutes. For these reasons, common process controllers are incapable of controlling this process.